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Solar panel set-up


Laura K

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Hi Everyone, 

 
I have a bit of a technical question on panels, how do I know what size MPPT is best for panels? I have a 50ft narrowboat and hoping to get through most of winter off-grid. Heres what Im thinking: 
 
4 x TRINA 325W ALL BLACK SOLAR PANEL
3 x VICTRON ENERGY 110Ah GEL DEEP CYCLE BATTERY
1 x VICTRON ENERGY MPPT 100/30 (would this be ok to use if the panels are 2 x 2 in parallel? Just dont want to have any risk of overloading the batteries) 
1 x VICTRON ENERGY PHOENIX 500W INVERTER
1 x VICTRON ENERGY BMV700 BATTERY MONITOR
 
Any tips or advice on whether this would be a well balanced set up would be great - Im open to any other choices out there too! Im in Ireland so Victron is the easiest brand to get a hold of
 
Thanks very much in advance to anyone who has advice on this, boat has space for at least 4 panels and is on east-west canal with good open sky. 
 
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You won't overload the batteries from charging because its the batteries that determine how much current they will accept after half an hour or so (typically).

 

Missing data - open circuit voltage of the panels. If the 100/30 means a maximum of 100 volts and up to 30 amps charge then if the panels are up to 35 volts open circuit your 2 in series and both series pairs in parallel will be OK (70 volts).

 

However  2 x 325 Watts at charging voltage gives a THEORETICAL maximum current flow of about 45 amps but as you are unlikely to get much more than half of that in the UK a 30 amp controller will probably do the job. In any case it is said that you can "overload" an MPPT controller current wise and they just lose the extra current.

 

I would be more concerned about you taking any percentage of charge reading from that monitor as gospel!

 

 

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You will need at least 2x and probably 3x that 'wattage' of panels to stand any chance of seeing you thru Winter. Winter is the time of maximum use (long dark nights etc) and minimum light (clouds, rain, low light levels, Sun low in the sky etc) so the number do not stack up.

 

You will not be physically able to fit enough panels on a NB.

 

Have you undertaken an electrical audit of how much you use in each season ?

If not do one. Then you know where you are starting from.

 

There are members here with widebeams and over 2,000 watts of solar that still need to run a generator in the Winter.

 

You would be better to spend the money on a proper boat installed water cooled diesel generator which will guarantee electricity whatever the weather.

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53 minutes ago, Tony Brooks said:

 

 

I would be more concerned about you taking any percentage of charge reading from that monitor as gospel!

 

 

Thanks very much Tony, really useful info - is there any other monitor you think might be a better bet? 

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3 minutes ago, Laura K said:

Thanks very much Tony, really useful info - is there any other monitor you think might be a better bet? 

 

Not really. That one is fine as long as you read and fully understand how to set  it up and very regularly recalibrate it. If you don't then things like Amp hours left and percentage charged will gradually tell larger and larger lies until you wreck those very expensive batteries. It will give you very reliable charging amps and voltage figures and with a bit of knowledge you can use tail current (amps) to tell when the batteries are more or less fully charged and what is known as rested voltage to infer state of charge. See the battery charging primer pinned at the start of the Maintenance Forum. A short while understanding and acting on that will handsomely repay you in longer battery life.

 

My personal view is that until a boater really understands how to look after their batteries, it would be far more cost-effective to use cheap 110 Ah open cell leisure batteries. Unless you can keep your batteries fully charged most of the time you will kill expensive ones as fast as cheap ones. Many here, myself included, consider batteries a service item that will need replacing every few years. Some people who can't or refuse to understand wreck new batters in weeks or a few months.

 

I am also concerned that 3 x 110 Ah lead acid batteries of any description are unlikely to be enough for a modern boat with a lot of electrical equipment. As Alan inferred, its the recharging to near fully charged at least one a week or more and 80% of fully charged every day that is the problem. Please do a power audit and post it here for comment. You also need to do the recharging estimations. Basic instructions on my website in the electrical notes, tb-training.co.uk.

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Have a look at this guy below on YouTube, he is good and does a lot of tutorials. You can read into it too much and get confused, I’ve just fitted 6x panels in series/parallel using the same MPPT and BVM using the shunt, also fitted the MPPT control monitor, all straight forward to fit and all accurate I’m finding. I would stick with Victron as these are fitted and recommended  by most installers that do boats.
 

https://youtube.com/c/EXPLORISTlife

Edited by PD1964
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15 hours ago, Tony Brooks said:

 

However  2 x 325 Watts at charging voltage gives a THEORETICAL maximum current flow of about 45 amps but as you are unlikely to get much more than half of that in the UK a 30 amp controller will probably do the job. In any case it is said that you can "overload" an MPPT controller current wise and they just lose the extra current.

 

The OP sates that they will have 4 x 325 Watts panels giving theoretical max of 1300 Watts or about 90 Amp at 14.6V. The Victron 100/30 is rated for max charging power of 440 Watts (30 Amp at 14.65 Volt). The installed panel power is 3 times the rated duty of the controller, in this case I would consider the 100/50 version which is rated at 50A charging current. On a sunny day with this set up you would be able to fully power the 500W inverter during the daytime and have power left over to charge the batteries at the same time.

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21 hours ago, Alan de Enfield said:

ou would be better to spend the money on a proper boat installed water cooled diesel generator which will guarantee electricity whatever the weather.

 

Undoubtedly true, but how much more expensive is a proper boat installed water cooled generator compared to the solar set-up the OP listed??

Genuine question

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8 hours ago, Col_T said:

 

Undoubtedly true, but how much more expensive is a proper boat installed water cooled generator compared to the solar set-up the OP listed??

Genuine question

A couple of times more expensive to install a generator, and sunshine is free not 90p per litre

 

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On 12/06/2021 at 12:53, Awayonmyboat said:

An alternative battery monitor is the Balmar SG200 - see the review at  https://marinehowto.com/category/electrical/

 

I fitted one about six months ago and have been happy with it so far.

 

 

 

I too have recently fitted a Balmar SG200, it's been in use for about 6 weeks now. Monitoring discharge seems fine but when charging the SoC seems to be inaccurate. It uses voltage & tail current to establish when 100% SoC is reached. The 'Time remaining' to 100% is currently useless - it'll frequently go from 6 hours to go to fully charged in 20 minutes.

I'm reluctant to start tinkering with the pre-set values, certainly until I've got a better idea of what's going on with it.

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On 12/06/2021 at 12:53, Awayonmyboat said:

An alternative battery monitor is the Balmar SG200 - see the review at  https://marinehowto.com/category/electrical/

 

I fitted one about six months ago and have been happy with it so far.

Why would you want to mix different manufacturers components when Victron do everything a good system requires?

  Victron do everything a good Solar set up requires and you can expand and upgrade with the same manufacturer at a later date. They have a good product line up and an informative internet site and are fitted and recommended by most boat solar fitters. Stick with all Victron.

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Posted (edited)

 

This was assessment from Bimbly, I guess main question would be whether that MPPT would still be good if I add more panels for winter - I could reduce amount needed by doing without fridge in winter - I would love to be 100% solar - Im one of those filthy environmentalists. Thanks so much everyone for all your tips so far, really so so useful as Im a beginner at this kinda thing

 

 

tem Quant Watts Hours Watt Hours
Laptop 35W X 1 35 W 3.0 Hrs 105 Wh
Laptop 45W Macbook Air X 1 45 W 3.0 Hrs 135 Wh
Smart Phone Charger X 1 5 W 9.0 Hrs 45 Wh
Rice cooker 14W X 1 14 W 1.0 Hrs 56 Wh
Bilge Pump Small X 1 30 W 4.0 Hrs 120 Wh
Pump - caravan water X 1 80 W 0.5 Hrs 40 Wh
Smart Phone Charger X 1 5 W 3.0 Hrs 15 Wh
Pump - caravan water X 1 80 W 0.5 Hrs 40 Wh
Fridge/Freezer A++ X 1 40 W 24.0 Hrs 960 Wh
Total Watt Hours
1,516 Wh
Sun Spec
Overspec by 100% with 3hrs of peak sun
Amp Hrs of Batteries
12v bank of 253Ah - 505 Ah
126 Ah per day of autonomy
Ah is quoted as usable Ah, if planning to use lead acid batteries to 50% DOD then double the Ah above.
Solar Panels - Watts
1,011 W
Solar Panels - Kw
1.01 Kw
Edited by Laura K
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8 minutes ago, Laura K said:

Thanks very much Tony, really useful info - is there any other monitor you think might be a better bet? 

 

All have their strengths and weaknesses, and all that basically count amps into the battery and amps out will be inaccurate unless you understand how to set them up to suit your boat and then regularly resynchronise them. Any that have been mentioned so far in this thread will give you very accurate amps and volts readings, and from those you can infer all you need to know once you learn how. I don't want to overburden you so am not going into that for now but just ask when you want to know but its all in that Battery Primer in the maintenance section.

 

There is another that works differently called a Smartguage but it overstates the degree of charge during charging but once charging has been stopped for a while gives decent state of charge reading at one time I would have recommended it but there have been too many cases of inaccurate  calibration from the factory for me to do it now.

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12 minutes ago, Laura K said:

 

This was assessment from Bimbly, I guess main question would be whether that MPPT would still be good if I add more panels for winter - I could reduce amount needed by doing without fridge in winter - I would love to be 100% solar - Im one of those filthy environmentalists. Thanks so much everyone for all your tips so far, really so so useful as Im a beginner at this kinda thing

 

 

tem Quant Watts Hours Watt Hours
Laptop 35W X 1 35 W 3.0 Hrs 105 Wh
Laptop 45W Macbook Air X 1 45 W 3.0 Hrs 135 Wh
Smart Phone Charger X 1 5 W 9.0 Hrs 45 Wh
Rice cooker 14W X 1 14 W 1.0 Hrs 56 Wh
Bilge Pump Small X 1 30 W 4.0 Hrs 120 Wh
Pump - caravan water X 1 80 W 0.5 Hrs 40 Wh
Smart Phone Charger X 1 5 W 3.0 Hrs 15 Wh
Pump - caravan water X 1 80 W 0.5 Hrs 40 Wh
Fridge/Freezer A++ X 1 40 W 24.0 Hrs 960 Wh
Total Watt Hours
1,516 Wh
Sun Spec
Overspec by 100% with 3hrs of peak sun
Amp Hrs of Batteries
12v bank of 253Ah - 505 Ah
126 Ah per day of autonomy
Ah is quoted as usable Ah, if planning to use lead acid batteries to 50% DOD then double the Ah above.
Solar Panels - Watts
1,011 W
Solar Panels - Kw
1.01 Kw

35W and 45W sound very low for laptops. And if you are running your bilge pump for 4 hours per day, something has gone seriously wrong. I should think mine gets about 10 minutes per month. And why are some items duplicated?

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14 hours ago, Laura K said:

 

This was assessment from Bimbly,

 

At a glance I'd say that your rice cooker is woefully underpowered - I'd suggest 140W at least.  It's an example of water heating which is best never done by electricity.  Also missing are (possibly) radio/tv, speakers, 4G modem/router, lighting.  Also, how are you heating the boat - anything other than a simple solid-fuel stove will use electricity to power internals....

I have about the same solar power (1250w) and consume about 1.2kWh/day - this setup suffices for about 10/12 months.  If I turn my fridge/freezer off then winter is mostly possible (my consumption reduces to 700Wh/day) , as long as the sun makes an appearance occasionally - but I do have lifepo4's, so charging is not so much of a lifestyle choice.

Edited by DaveP
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I see a fridge on the list, unfortunately I doubt a 500 watt inverter will start the compressor motor, these typically take 10 times the running power for a few seconds, most people find anything under 1000 watts is unlikely to be able to start the motor and really 1200 watts to be reliable (the standby current for a good inverter will only be a a few hundrd milliamps more than a 500W)

 

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On 14/06/2021 at 20:12, David Mack said:

35W and 45W sound very low for laptops. And if you are running your bilge pump for 4 hours per day, something has gone seriously wrong. I should think mine gets about 10 minutes per month. And why are some items duplicated?

Depends on usage. My relatively high spec 15” Lenovo pulls over 100w when charging its battery with the CPU and GPU working hard rendering a video and the screen on full brightness, but under 10w when doing web stuff/emails with a charged battery. 

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In the estimate of power needed, the fridge estimate is too high for daily use. The fridge will have its duty cycle on/off periods. The figure used (960 Wh), rounded up, is 365 Kwh a year. The figure should be around half of the estimated. A decent under counter larder fridge can achieve under 100 Kwh a year. 

 

 

Edited by Higgs
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